Full-duplex cellular system is introduced to increase capacity of cells. In the full-duplex cellular system, the base station of a cell works in a full-duplex mode where the base station simultaneously transmits and receives in the same frequency at the same time. The base stations of different cells usually work in the same frequency. In the full-duplex cellular system, a user equipment (UE) communicating with the base station (BS) may also work in a full-duplex mode. A patent application WO2013004283A1 provides a full-duplex cellular solution. According to this solution, a UE measures received signal characteristics from at least one other UE when the other UE is transmitting signals, and the measured received signal characteristics is comprised in measurement data. The UE transfers the measurement data to a BS, then the BS uses the measurement data for scheduling transmission of signals and reception of signals from and to the BS such that each UE that communicates via the BS either transmits signals to the BS using a first frequency interval or receives signals from said BS using the first frequency interval, and the BS transmits signals and receives signals simultaneously using the first frequency interval.
Due to the use of same resources blocks in uplink and downlink, extra inter-cell interference and intra-cell interference exist and would limit the capacity gain that can be reaped from the full-duplex designs. The extra interference caused by full-duplex designs has been elaborated in table 1.
TABLE 1Extra interference caused by full-duplex cellular systemItemInterferenceAggressorVictim1Intra-cellBS downlink transmissionBS uplink reception2Intra-cellUE uplink transmissionUE downlink reception3Inter-cellBS downlink transmissionBS uplink reception4Inter-cellUE uplink transmissionUE downlink reception
The intra-cell interference between BS downlink transmission and uplink reception may be reduced by self-cancellation of the BS. The inter-cell interference between downlink transmission and uplink reception of different BSs may be reduced by downlink power control and beam-forming solution. For the intra-cell between uplink transmission and downlink reception of different UEs within a same cell, a patent application WO2013107139A1 discloses a solution to reduce such interference. According to this solution, the BS obtains the interference degree when the BS and at least two UEs perform full-duplex transmission. Then the BS determines a UE capable of performing uplink and downlink signal transmission over the same time-frequency resource among the at least two UEs, according to the interference degree. In one example, the interference degree is determined based on the location information of UEs.
For inter-cell interference between uplink transmission and downlink reception between UEs of different cells, it is difficult to use the above solutions to reduce or eliminate the inter-cell interference. Therefore, a new method is needed to reduce the inter-cell interference between uplink transmission and downlink reception of UEs served by different BSs.